Fibrous, non-woven fabrics, mats, and papers have found particular utility for providing dimensional stability, fire resistance and flexural strength. The use of glass fibers in paper making has long been known. Glass fiber paper was produced on production equipment as early as the 1930's. Since that time, very fine blown micro-fibers, glass fibers and even glass flakes have been used to produce specialty papers. These papers have been produced in all-glass form and in ad-mixes with cellulose, and other fibers. The use of micro-fibers and glass fibers alone or in combination with other fibers for high temperature filtration or controlled porosity is disclosed in the prior art. Also disclosed, is the use of glass fibers and wood pulp to control dimensional stability. Composites panels having foam cores with fibrous mats on one or opposite surfaces of the core also are known. Roofing insulation often embodies a composite panel comprising an organic foam core with an inorganic fibrous mat on the upper and lower surface thereof. The industry refers to the mats as "foam facer mats" and refers to the composites as "rigid foam insulation."
I have invented a new foam facer mat which uses a blend of glass fibers and wood pulp fibers to control the porosity of the mat. The amount of cellulose fiber required to achieve the desired low mat porosity is strongly influenced by the cellulose fiber length and the degree of fibrillation of the cellulose fiber. An accepted measure of cellulose fiber length/fibrillation is the "Canadian Standard Freeness" of the pulp.
Many closed-cell organic or plastic foams particularly polyurethanes, have excellent insulating properties. However, such foams are commonly lacking in dimensional stability particularly when subjected to non-uniform temperatures. In addition, the facings required in the manufacturing process can exacerbate these tendencies. Such characteristics have rendered these organic foams less than suitable for roof insulation particularly when placed on layers of hot asphalt applied on the underlying roof structure and when hot asphalt is applied over the foam.
By employing layers of inorganic fibers on one or both major surfaces of a foam core or slab, the changes in dimensions of the foam in aging tests are reduced to a small percentage of the former changes encountered. The inorganic fibers employed are preferably glass fibers, having high strength and a high modulus of elasticity, and at least one of the layers of fibers preferably is in the form of an nonwoven mat, being randomly disposed in a plane parallel to the core.
An effective method of achieving the structural integrity is to place the fibrous layers in contact with the foam forming the core during foaming so that the foam will tend to penetrate interstices in the fibrous layers to form an interlocking inter-face therebetween. For this purpose, a suitable organic foam mixture can be applied to one of the fibrous layers with the other fibrous layer then placed on the foaming mixture and backed up or supported so that it will not be able to move completely freely outwardly from the first fibrous layer as the mixture foams. This achieves penetration by the foam into both layers. The inorganic facings restrain dimensional changes in the foam when subjected to changes in temperature and moisture. This substantially reduces warping and cell rupture of the foam.
More specifically, the first fibrous layer can be moved in a flat, supporting position on a belt-type conveyor above which is suitable mixing apparatus and a nozzle or nozzles, the nozzle(s) evenly distributing the foam mixture onto the first fibrous layer. The second fibrous layer is then directed onto the foam mixture, preferably after the foaming has commenced. A second belt-type conveyor is then disposed above a portion of the first conveyor a predetermined distance, with the second conveyor backing up and restricting upward movement of the second fibrous layer as foaming of the mixture moves the second layer upwardly. A composite panel thereby results consisting of the organic foam core or slab and the two fibrous layers located in substantially parallel relationship, with this panel being cut or shaped to any desired size and predetermined configuration.
Specifically for use in roof installation, a polyurethane foam slab is employed having a mat of fibers on the upper surface thereof and a layer of fibers on the lower surface. The lower layer can be in the form of a board of fibers or a mat of them, similar to the mat on the paper surface of the slab. Whether the bottom surface is thicker board or a thinner mat depends primarily on the nature of the underlying roof structure and whether or not the roof insulation must be fire retardant or resistant. In either case, the core with the inorganic fibrous layers on the surfaces produces a balanced system which has many advantages over insulating structures heretofore known, particularly in achieving dimensional stability with reduction in warping and cell rupture of the foam.
The use of chopped glass fibers is well known. The chopped glass is produced in the form of individual strands which are sized, gathered into rovings and chipped to a desired length. Various fiber diameters have been evaluated with K.times.1/2" being preferred on a cost effectiveness basis. K fibers refers to the diameter of each filaments and is 13.5 micro meters. Glass fibers used in the practice of this invention can be, but are not restricted to "E" glass fibers, well known to those skilled in the art. Such fibers are described in U.S. Pat. No. 2,334,961.
The facers described in the disclosure relies on two types of physical attributes to obtain "foam hold-out", i.e. control foam bleed through.
The pore structure of the mat which is controlled by the fiber input to a large extent and is defined by the air-permeability of the mat.
The low surface energy of the binder system which is achieved through the use of a fluorocarbon "antiwetting" agent. The low surface energy prevents the foam from wetting the surfaces of the pores. Smaller pores do not require as low a surface energy to prevent wet-through of the mat as do larger pores.
The Canadian Standard Freeness (CSF) is a measure of how "slow" a paper stock is, i.e., how much the stock retards the drainage of water during the forming of the stock into a paper web. The lower the CSF the more closed and dense the paper structure. The CSF is controlled by both the length of the fiber and the degree of fibrillation of the fiber.
The structures of my invention have an air-permeability of less than 150 cubic feet per minute per square foot (CFM/SF). When using air through drying systems a practical lower limit of mat air-permeability is 50 CFM/SF as below 50 CFM/SF, the structure is too dense for practical drying. Generally, the mat has an air permeability ranging from 50 to 150 CFM/SF.
The foam facer mats that make use of the fluorocarbon anti-wetting agent are acceptable for mechanically fastened and ballasted roofing systems, but at this time are not considered acceptable for fully adhered systems. Apparently, the fluorocarbon antiwetting agent changes the foam cell structure right below the facer such that even though the 90 degree pull, facer adhesion test is "good" the facer can be peeled off the underlying board when the force is applied so a shear is applied to the foam cell structure. Shear loads can be applied to the facer/foam interface by stress induced by temperature changes seen in normal use as well as various kinds of "application" damage.